Lower South Island Dry Summer Studies

Transpower, as the system operator, has duties to monitor and analyse security of supply, under varying hydro-storage conditions. Our process includes monitoring inflows and hydro storage, analysing worst-case scenarios, and identifying ways to manage and alleviate possible problems.

In January 2018 storage levels in the South Island started to plateau due to low inflows, which increased the probability of crossing the Hydro Risk Curves (HRC); where hydro demand is not being sustainably met. As Manapouri lake levels declined below the main operating range, we undertook analysis to identify any potential security of supply problems the grid would experience if the dry conditions were to continue.

General Information

Our analysis:

  • identified the minimum voltage support required from generators to prevent voltage stability issues within Southland.
  • analysed the transmission constraints on Southland power import and the minimum generation required in Southland.
  • considered the effects of implementing Variable Line Rating on potentially thermally constrained circuits and splitting the Gore 110 kV Bus.

Study Report

2018 Lower South Island Dry Summer Report [ pdf 950.35 KB ]